| Angle () | CG | ND1 | CE1 | NE2 | CD2 | § |
|---|---|---|---|---|---|---|
| ND1 protonated | ||||||
| EH91 | 105.2 (10) | 109.0(17) | 111.7 (13)† | 107.0 (30) | 109.5 (23) | 542.4† |
| EH99 | 106.0 (14) | 108.2 (14) | 109.9 (22) | 106.6 (25) | 109.2 (19) | 539.9 |
| PDB, no metals | 105.2 (9) | 108.3 (8) | 110.9 (14) | 105.8 (17) | 109.7 (15) | 539.9 |
| PDB, metals‡ | 105.5 (8) | 108.4 (8) | 110.4 (12) | 106.4 (14) | 109.3 (12) | 540.0 |
| PDB, all | 105.5 (8) | 108.4 (8) | 110.4 (12) | 106.4 (14) | 109.3 (12) | 540.0 |
| CSD, no metals | 104.8 (5) | 107.7 (3) | 111.8 (3) | 104.7 (5) | 111.0 (7) | 540.0 |
| CSD, metals‡ | 105.1 (4) | 108.2 (4) | 111.2 (6) | 105.3 (5) | 110.2 (5) | 540.0 |
| CSD, all | 105.1 (5) | 108.1 (5) | 111.3 (6) | 105.3 (6) | 110.3 (6) | 540.1 |
| NE2 protonated | ||||||
| EH91 | 109.2 (7) | 105.6 (10) | 111.7 (13) | 106.9 (13) | 106.5 (10) | 539.9 |
| EH99 | 109.2 (7) | 105.7 (13) | 111.5 (13) | 107.1 (11) | 106.7 (12) | 540.2 |
| PDB, no metals | 108.2 (11) | 106.4 (14) | 110.9 (14) | 107.6 (9) | 106.8 (6) | 539.9 |
| PDB, metals‡ | 107.9 (10) | 106.8 (11) | 110.3 (9) | 108.1 (8) | 106.9 (8) | 540.0 |
| PDB, all | 108.1 (11) | 106.5 (14) | 110.7 (13) | 107.8 (9) | 106.9 (7) | 540.0 |
| CSD, no metals | 109.2 (8) | 105.2 (8) | 112.1 (8) | 107.1 (7) | 106.5 (7) | 540.1 |
| CSD, metals‡ | 108.7 (6) | 105.8 (7) | 111.2 (6) | 107.8 (7) | 106.4 (8) | 539.9 |
| CSD, all | 109.1 (8) | 105.3 (9) | 111.9 (10) | 107.2 (8) | 106.5 (7) | 540.0 |
| ND1 and NE2 protonated | ||||||
| EH91 | 106.1 (10) | 109.3 (17) | 108.4 (10) | 109.0 (10) | 107.2 (10) | 540.0 |
| EH99 | 106.1 (8) | 109.0 (10) | 108.5 (11) | 109.0 (7) | 107.3 (7) | 539.9 |
| PDB, no metals | 106.2 (4) | 109.0 (7) | 108.7 (6) | 108.5 (7) | 107.7 (4) | 540.1 |
| CSD, no metals | 105.9 (5) | 109.3 (5) | 108.4 (5) | 108.9 (6) | 107.4 (5) | 539.9 |
| ND1 and NE2 deprotonated | ||||||
| CSD, metals | 107.2 (7) | 104.8 (7) | 114.0 (8) | 104.3 (6) | 109.7 (4) | 540.0 |
| PDB resolution 3.0, all | 106.3 (8) | 109.2 (9) | 108.5 (7) | 108.9 (6) | 107.1 (5) | 540.0 |
†
These values seem to be in error. The corrected value for the EH99 NE2CD2 bond length is 1.372 and that for the EH91 CE1 angle is 109.3, giving the sum = 540.0.
‡
In metal complexes, ND1 is protonated when NE2 is metal-coordinated and vice versa.
§
Sum of the endocyclic valence angles (expected to be 540.0 for a planar five-membered ring).